Industrial scale fermentations were historically performed for solvent and acid production prior to the rise of the petrochemical industry. Concerns about pollution, climate change, and resulting environmental degradation have renewed interest, particular where low cost or waste biomatter are available as feedstock. One problem that economically constrains more widespread adoption is the high energy expenditure required to recover fermentation products from the low concentrations typically seen in fermentation broths. Efforts to increase product concentrations in fermentation broths have met with limited success owing to the toxicity of these compounds to the cultured microorganisms. Another issue which constrains the economic feasibility of fermentation based bioproducts is the productivity of the fermentation process. Increases in productivity lead to an improved use of installed capital.
The present invention details the surprising discovery that strains, environmental isolates, or mutants of product producing microorganisms can be adapted or selected for their simultaneous ability to grow on solid support and tolerate high concentrations of a product and that these strains, environmental isolates, or mutants of product producing microorganisms retain the higher product tolerance in culture if they are immobilized on a solid support rather than cultured as a suspension culture. Higher product concentrations are now possible that improve overall culture productivity and reduce energy usage. Increased product tolerance may rely on decreased inhibitory effect by known inhibitory agents such as HMF, fufural, levulenic acid, glucoronic acid or acetic acid, which may be generated by the organism or be present in the initial feed.